The VNH5019 shield can be used to drive a stepper motor. However, I cannot say if it would be appropriate for your stepper motors without knowing how much current they draw (the NEMA number only refers the physical size of the stepper motor). You can find sample code for using our MC33926 shield as a stepper motor driver that also works with our VNH5019 shield in this post (you will have to comment/uncomment some lines in the code).
Stacking shields might work; however, I suspect it would be really difficult. It would require remapping some of the pins and modifying the library to use different timers for the additional shield.